The subject of the invention is a process for the separation of iron from an organic solution containing uranium.
More generally, the invention relates to a process for the extraction of uranium present in phosphoric acid solutions, especially in phosphoric acid solutions obtained from phosphate ores containing iron.
It is known that phosphate ores generally contain quantities of uranium which may be recovered during the treatment of phosphate ores with sulfuric acid.
This recovery is worthwhile, considering the large tonnage of phosphate ores treated with sulfuric acid.
During the treatment of ores with sulfuric acid, uranium passes into solution in the phosphoric acid obtained and processes for recovering uranium from the phosphoric acid employ suitable organic solvents such as those described in French Patent No. 2,369,803, which consist of a synergetic mixture of extractants.
The process developed using these solvents enables uranium to be extracted and purified in a single cycle, and iron is removed from the decanters in the form of a precipitate, when uranium is reextracted using ammonium carbonate.
New solvents, described in French Patent No. 2,442,796, certificate of addition No. 2,459,205 and French Patent No. 2,494,258, have also been developed.
These new solvents consist of stronger synergetic pairs. These new solvents extract larger amounts of uranium, but they also extract more iron, which makes the alkaline reextraction of uranium difficult, because of the undesirable presence of iron hydroxides which precipitate in an alkaline medium.
The use of organic solvents such as trioctylphosphine oxide and di-2-ethylhexyl phosphoric acid with dilute and substantially iron-free phosphoric acid has also been envisaged, but this process has the disadvantage either of bringing about a significant coextraction of uranium with the iron and therefore a loss of uranium which passes into the aqueous phase, or of having to operate in a dilute phosphoric acid medium which subsequently makes it necessary to reconcentrate the phosphoric acid or results in a loss of the latter (cf. French Patent No. 2,459,837).
The subject of the invention is a process for the extraction of uranium from an organic solution containing it and contaminated with iron.
One of the aspects of the invention is to provide a process for the separation of iron contamination an organic solution containing uranium, which process also enables uranium to be extracted at a high rate.
One of the other aspects of the invention is to provide a process which enables solvents capable of extracting uranium with a high yield to be used with ease, while eliminating the problems caused by the presence of iron.
One of the other aspects of the invention is to provide a process for the extraction of uranium which only comprises a single extraction-reextraction cycle, which avoids a second purification cycle and the dual operation of reduction-oxidation to reextract uranium, while overcoming the difficulties of carrying out the operation of direct alkaline reextraction of uranium.
One of the aspects of the invention is to provide a process for the separation of iron contaminating an organic solution containing uranium, which process does not require the valency of the uranium or that of the iron to be changed at any time.
One of the aspects of the invention is to provide a process for removing iron from or de-ironing phosphoric acid, which can be applied industrially and which can advantageously be integrated into a plant for the manufacture of phosphoric acid from rock phosphates, in which it is also desired to recover the uranium contained in the acid phosphates.